As a mobile broadband (MBB) develops and a quantity of users increases, a network capacity is becoming a bottleneck of development of a universal mobile communications system (UMTS). A common manner of expanding the network capacity mainly focuses on networking with the addition of a spectrum, a station, or multiple sectors, or using of a dual-beam antenna. A quantity of main device channels is increased in the dual-beam antenna to increase a quantity of partitions of service information channels in terms of a vertical dimension, so as to improve spectral efficiency, and further increase the network capacity.
When a dual-beam antenna is applied to a Long Term Evolution (LTE) technology, a radio-frequency system of a base station has an increasingly high requirement for a technology of a base station antenna, and in particular, for passive inter-modulation (PIM). PIM is an inter-modulation effect caused because passive components such as a joint, a feeder, an antenna, and a filter are non-linear when these components work in a case of a multi-carrier high-power signal. It is usually considered that passive devices are linear. However, the passive devices are non-linear to different extents in a high-power state. Such non-linearity is mainly caused because a joint of the passive devices is not tight, or the like. Due to the non-linearity of these passive devices, higher-order harmonic waves relative to an operating frequency are generated. These harmonic waves mix with the operating frequency to generate a new set of frequencies, and finally generate a set of unwanted spectrums in the air. Consequently, normal communication is affected.
Currently, in design of a base station antenna, a bridge in a splitting network circuit usually uses a microstrip structure in a printed circuit board (PCB), and a phase-shift circuit usually uses a strip line structure on the PCB. The splitting network circuit and the phase-shift circuit are usually separated, and often cascaded in a manner of cable welding or screw connection. FIG. 1 is a schematic block diagram of a manner of connection between a splitting network circuit and a phase-shift circuit in a feeding network of a dual-beam antenna. Such a cascading manner increases a quantity of passive components, and there are risks such as a loose joint of passive components. Consequently, a PIM indicator of the dual-beam antenna is affected.